This invention relates to a method of texturing the surface of a glass substrate for a magnetic disk and more particularly to a method of chemical mechanical texturing for a surface of such a glass substrate.
The substrate of a magnetic disk has its surface mirror-polished first and then has it textured so as to have a specified surface roughness. The purpose of texturing is to form line marks on the substrate surface such that when it is used with a magnetic head, the floating distance of the magnetic head from the disk surface can be maintained dependably constant while the disk is rotating at a fast rate and also such that the magnetic head can be prevented from becoming adsorbed to the disk surface while the disk is stationary.
The texturing is usually carried out by supplying a suspension mixed with minute abrasive particles of diamond or alumina to the surface of the substrate while the latter is rubbed with- a woven or unwoven tape or a tape with planted piles. Textured line marks can thus be formed as these abrading particles are pressed on and rubbed against the substrate surface to mechanically grind it. Such a process for forming line marks is usually referred to as the chemical mechanical texturing.
Recently, glass substrates are coming to be used as commonly as substrates made of an aluminum alloy for producing magnetic disks, and these glass substrates are also required to have their surface or surfaces textured for the same reasons, that is, such that the floating distance of the magnetic head can be reduced and hence that the recording density of the magnetic disks as memory media can be increased.
Since glass substrates are hard, however, it has been considered difficult to form sufficiently minute and uniform line marks on a glass substrate by a mechanical texturing process,
It is therefore an object of this invention to provide a chemical mechanical texturing method by which minute and uniform line marks can be formed on the surface of a glass substrate for a magnetic disk.
The chemical mechanical texturing method embodying this invention, with which the above and other objects can be accomplished, may be characterized by the steps of pressing a woven cloth tape made of plastic fibers against a surface of a glass substrate and causing it to run thereover while supplying thereonto a suspension containing abrading particles and a solution which contains hydroxyl groups.
If a method according to this invention is used, the solution in the suspension containing hydroxyl groups causes a solid phase reaction on the contact boundary surface between the abrading particles in the suspension and the surface of the glass substrate, thereby generating over this surface a substance which is different and the texturing process is carried out while this boundary surface portion is chemically and mechanically removed. Since the method makes use of this chemical reaction on the surface of the glass substrate caused by the solution containing hydroxyl groups in the suspension, deterioration or degradation due to the process is negligible and since work units of the process are extremely small, it is possible to form extremely small line marks.
The solution in the suspension containing hydroxyl groups serves not only to accelerate the chemical polishing process due to the solid-phase reaction which takes place over the contact surfaces between the abrading particles and the substrate surface but also as a coolant, absorbing the heat of friction due to the mechanical grinding process between the abrading particles and the glass substrate.
Examples of solution containing hydroxyl groups suitable for the purpose of this invention includes KOH and NaOH solutions.